Figure 2.

SEM views of local PoSi regions fabricated in a 20-mΩ cm p-type (111) silicon substrate. Slice-tilted (on the left) and top (on the right) views of local porous regions were performed by SEM. The anodization was performed at 28 mA cm⁻² for 45 min in a HF (30 wt.%)-acetic acid (25 wt.%) electrolyte. The depth of the locally produced PoSi region is 80 μm. A 60-μm under-mask etching was measured.